Parents upset after testing revealed higher than normal lead levels in a Chicago elementary school questioned Chicago Public Schools officials Tuesday on why such testing hadn’t been done sooner.

CPS CEO Forrest Claypool, along with a panel of experts, fielded the questions from concerned parents at Tanner Elementary.

Tanner Elementary School was one of 32 schools tested as part of a pilot program in the district and was the only school where elevated lead levels were detected. Water from three water fountains in the school tested positive for elevated levels of lead, the district announced last week.

“How long has this problem been going on?” said parent Karen Britt. “You’re all just now testing it? You all should have been testing these schools for this not just now.”

District officials said they have always complied with guidelines from the Environmental Protection Agency, but recently decided to conduct testing in wake of the crisis in Flint, Michigan.

Experts at the meeting told parents that sewer construction outside the school was not the cause of the elevated lead levels, but noted the three water fountains in question were removed and students are now being provided with bottled water.

The Chicago Health Department said it plans to bring a mobile lab to the school next week to conduct lead testing on any child whose parent requests it.

“If your test results come back positive, we will contact you and we will encourage you to go to your child’s pediatrician to get a second test to make sure that it’s accurate,” said Dr. Cort Lohff, medical director for environmental health with the Chicago Health Department.

CPS officials have said they plan to test every source of drinking water in the district.